River Restoration Enters the Planting Phase

River restoration project at The Morton Arboretum
The DuPage River is undergoing significant restoration efforts.
October 28, 2016

The earth movers are gone. Now, it’s time for plants.

Restoration along the East Branch of the DuPage River in The Morton Arboretum is proceeding on schedule, according to Kurt Dreisilker, head of natural resources.

This year, “we got through the biggest phase of visible work that will be done,” he says, referencing the disposing of invasive trees, shrubs, and other plants, and moving earth to create gently sloped banks in the stretch west of Illinois Route 53.

This fall, contractors working on the project for the Arboretum and U.S. Army Corps of Engineers have begun replanting the 72 acres along more than a mile of river. They’re scattering a mixture of seeds of native plants, such as blue flag iris, prairie cordgrass, swamp milkweed, New England aster, and water willow (not a tree, but an aquatic plant).

The various kinds of plants will sort themselves out, with each species sprouting and thriving where conditions are best for it. Next year, they’ll be joined by some young trees and shrubs.

Along the stretch east of Route 53, in the Asian and Eastern U.S. Wetlands collections, brown areas of dead undergrowth still show where turfgrass and invasive plant species were destroyed. Over the next year, that brown will disappear beneath the green sprouts of native plants.

“From now on, we will expect the native species to grow and the invasive species to decline,” Dreisilker says.

Of course, invasive plants will continue to invade or sprout from seeds hidden in the soil. For the next four years, until the native plants are well enough established to crowd out any interlopers, workers will continue to remove invasive plants along the river.

Some subtle technology is helping the new native plants on the West Side. Around Lake Japomaca, the shore has been spread with sheets of mesh, extending down into the water. This webbing protects seeds and young plants from animals, such as carp and ducks, until they get established.

As the plants grow, they’ll hide the mesh.

“It will disappear,” Dreisilker says.

The same mesh was used to establish native plants around Meadow Lake in 2004 and 2005.

Along the river’s new sloped banks, tan mulch blankets made of biodegradable jute temporarily cover the soil and seeds to protect them from erosion and animals. Over time, microorganisms in the soil will break the jute down like leaves in a compost pile.

East of Route 53, the river banks haven’t been reshaped to make slopes. Instead, the banks will be protected from erosion by structures that have been installed to divert the current away from vulnerable areas. Once the new plants are established, their deep, intertwined roots will help stabilize the banks, Dreisilker says. Clumps of tree roots and boulders placed in the river itself also will break up the currents.

In the water just off the Eastern U.S. Wetlands Collections, a rocky area has been constructed on the riverbed to make little ripples that will creating good habitat for fish and other aquatic animals. Other native animals will find homes among the roots and boulders and in the plantings along the river’s edge.

“The project has gone pretty well as planned, with no significant delays,” Dreisilker says.

With the big, noisy machines gone, the remaining work will be quiet and unobtrusive. The only signs will be the hopeful new plants in spring.